VS 2010 Backgroundworker Thread Running Faster Than The UI Can Update Progress?
Nov 15, 2011
I have a VB.NET 2010 app that uses a backgroundworker to process MS Word docs. All of the code does what it is supposed to do, except when my code calls ReportProgress(). The UI cannot process the ProgressChanged event fast enough before the values in the class that are passed are changed. I know this because I inserted a System.Threading.Thread.Sleep(100) line after each ReportProgress() call which allows time for the UI to make the updates properly. I guess I am looking for a better solution thanThread.Sleep(100) since this adds to the amount of time it takes to process all of the files. Here are some snippets of code that I am using:
[Code]...
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Jan 2, 2012
I am using the BackgroundWorker to do the heavy tasks so the UI thread doesn't get blocked. While the BackgroundWorker can send values to the UI thread using the progress-scheme, how can the BackgroundWorker get some values FROM the UI thread?
Either by asking it or simply by the UI thread sending some values to the BackgroundWorker?
Just accessing a variable of the UI thread like UIForm.x within the BackgroundWorker does not work, it does not seem to have access to the UI variables?
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Apr 11, 2012
I've made an application which goes through a long procedure when a button is clicked. I don't want the user to think the program has frozen, so I'd like to add a marquee progress bar just to show that it's still running. However, if I simply add the progress bar and make it visible when the button is clicked, the bar will appear but freeze and wait for the procedure to finish before it starts scrolling.
I know this is due to both the procedure and the progress bar running on the same thread, but the tutorials I've seen on getting a process to run on another thread seem confusing. What is the simple way to make a progress bar run on a separate thread?
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Dec 23, 2009
Say I have a code with 3 methods that do some pretty intensive work. Would executing these methods on 3 seperate threads be faster then executing them one after the other on a single core cpu? And what if it's a dual core or HT?
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Jan 26, 2012
I have build a VB.Net windows application which does uploads data into database and basically updates two controls:
1. A textbox which is constantly updated with one line per database record upload.
2. A label which keeps track of the count of database record uploaded.
I have used BackgroundWorker thread concept, where the thread's bgwWorker_DoWork() method contains the business logic for upload and bgwWorker_ ProgressChanged() updates the 2 UI controls based on uploads.But the issue I am facing is that I do not get complete updates on both the UI controls. Sometimes the thread bypasses update of textbox and sometimes of label. I could resolve this issue by adding System.Threading.Thread.Sleep(25) before each UI control update code.[code]
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Sep 5, 2010
I have some issues with background worker progress reporting functionality. I'm implementing a progress indicator and even if I marked the backgroundworker as report progress (true), it won't report progress until it finish the job.
The code is like this:
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
action_1()
[code]....
The result is as expected (label1 with 100 value) but only when worker finished all the steps. If I'm triggering a messagebox in ProgressChange I see two message windows at the end of DoWork handle.
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Apr 27, 2010
i have a standard login form that allows the user to enter username and password and click OK or cancel. I have a progress bar called pbLaunch with the visible property set to false and the animation set to marquee. when the user clicks OK i would like to run a separate thread called bgwProgress that makes the progress bar visible and fires up the marquee just to show that something is happening while form1 loads up.....so far i'm stuckn the ok click event i have the following:
Try
Dim bgwProgress As New System.ComponentModel.BackgroundWorker
bgwProgress.WorkerSupportsCancellation = True
[code].....
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Nov 14, 2011
I tried to update the button text on a form from a backgroundworker.do_work event, and it failed, with the usual cross-thread exception message.However, by pure chance, I also tried to update text in a system.windows.form.toolstripstatuslabel also from this backgroundworker.do_work event, and it DOES work. Question: why is this? Is it perhaps because theres some kind of implicit shared behaviour with system.windows.form.toolstripstatuslabel?
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Dec 19, 2010
I am running a test program for VB.NET, and it will simply crunch a million numbers in for loop. I've linked a variable implying the progress of the for loop with the progress bar, but it seems that when I run the program, the progress bar does not update itself. The bar itself has only value 0-100 as input (as stated in the document) and I've tested it without using the for loop, and it works.
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May 3, 2012
I have several reports that all merge onto the same datatable. The user can click several to run and then hit the 'find records' button to run them all simultaneously. Since they each take so long, I'd like to update the user on the status bar as each of these stored procedures is called successfully. However, when I call the procedure, i only get one update at the very end listing evertyhing.
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Sep 15, 2011
I am having trouble accessing the main thread (my form) when calling thread is running in a class (or module). I have no problem to manipulate a data (in a thread) from a form, the textbox can be updated using delegate and invokerequired but it doesn't seem as easy when the thread that processes a variable is handled by a thread that is running in a class.
[Code]...
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Jul 5, 2011
I have a backgroundworker that is downloading data from different webpages and process them to a datagridview.I get the Cross-thread operation not valid error on the first For loop.
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
dim i as integer
tot = (numPostnrTo.Value - numPostnrFrom.Value) / 10
[code]....
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Feb 17, 2012
Would anyone be able to help me here please. I'm fairly new to VB.net and threading so im just trying to figure out what is happening.When I debug this I am getting the error thread operation not valid: Control 'ProgressBar1' accessed from a thread other than the thread it was created on.
I'm a little lost as to why the error is occuring or how to fix it. I've had to put the progress bar in a separate thread otherwise the GUI crashes
[Code]...
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Jul 1, 2010
A BackgroundWorker thread can pass data to the primary thread. It does it via the RunWorkerCompleted and ProgressChanged events, which I believe run in the primary thread. I would like to encapsulate the BackgroundWorker control in a class so that I can instantiate it more than once. But I don't know how the BGW can then communicate with the primary thread. If the BGW control is within a class, it does not have access to the properties outside the class. In that case, how can the BGW pass data to the thread that instantiated it?
[Code]....
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Aug 4, 2011
I'm working with BackgroundWorker, I want the BackgroundWorker do the retrieval process of data from database while the user can still do another task on the form. The problem is, after retrieving the data, I can't seem to access the ListView in my Form from the DoWork event of BackgroundWorker, I will populate that ListView using the data I've retrieved.
Consider this example, this is how I'm doing it:
Public Class Test
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
[Code].....
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Sep 4, 2009
How do run processes synchronously from a thread or backgroundworker thread? Is it even possible?We have program that allows the user to download several files from a remote server, compress them, and then email the files.It has several long running processes that must run in order. We want these to run on a separate thread so as not to make the form unresponsive. Does a way exist to do this? We attempted a rather clumsy way of approaching this problem by using background worker threads. When each thread is completed and returned back to RunWorkerCompleted, we start another background worker thread and repeat the the next process. It works somewhat but seems to take a lot of resources to run.
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May 22, 2011
I want to execute a few external apps, where in between a RichTextBox gets updated.. Say when program1 has been startet the RichTextBox is updated.. And when program2 has been startet the RichTextBox is beeing updated again.So what i've done so far is this:
Public Class Form1
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
[code]....
But when doing the above i get the following error:
Quote:
Cross-thread operation not valid: Control 'RichTextBox1' accessed from a thread other than the thread it was created on.
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Nov 12, 2009
Preface: I know this is an unusual/improper way to do this. I can do this with a "real" ShowDialog(), background worker/thread, and so on. I am trying to do specifically what I describe here, even if it is ugly. If this is impossible for X reason, I have created a fancy progress dialog for some of our long running operations. I need to have this dialog shown on a new thread while having processing continue on the calling (UI in most cases) thread.
[Code]...
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Jan 14, 2011
I have on timer thread that needs to pass every time a different data to another running thread to make the calculations.
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Aug 13, 2011
Currently, I'm testing the timer function.
I used the following code for my form:
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[Code].....
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Jul 7, 2010
get the progress bar show the progress of the batchfile running in the background?
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Jan 6, 2010
I am using backgroundworker thread in my app. I also have a class in my project and am able to updated the user UI from the form, but most of my time consuming operation happens in the class so I tried to do an update like this Form1.BackgroundWorker1.ReportProgress(4, strname), but I get an error that say that the backgroundworker is not set to report progress.
I have this set in the load event for the app.Are you not able to call form items like this from a class?
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May 22, 2012
trying to show 'loading' text while performing selectedindexchanged with backgroundworker
but it is hang in 'loading' and result does not show :(
Private Sub cbPortNo_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbPortNo.SelectedIndexChanged
[Code]...
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May 23, 2011
I have created a simple Backgroundworker process to copy a large file (30GB). Is there any way to report the progress of that file copy?
I'm using System.IO.File.Copy to perform the copy. I've seen a few posts/blogs that suggest comparing the bytes copied with the size of the source file but that seems like a huge overhead in this case.
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Feb 13, 2011
I have a few subs that run under Webbrowser1.document completed section of my app I know the code words because I tried it out using a new project and tied the code to a button and it works great. After stepping into my code during run time it appears that the app is trying to call my sub before the next page appears. What would be the way to place a pause on the Thread so that the web page can catch up before running the next sub?
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Feb 3, 2009
Got a bit of a weird problem with a progress bar. I'm using a backgroundworker, which calls a "Process" function in a different class. The function goes about its business, and sends an update back to the form displaying the progress bar. What I'm finding is that its doing everything right, except update the progress and a label on the form. I've put breakpoints in to check the values of variables being sent to the form, and they're correct. I've also checked the value/maximum of the progress bar during the same break as I step through, and they're being set correctly.
they're just not displaying their updated status. I've tried refresh and application.doevents, to no avail. When the backgroundworker is complete, the values of the progress bar/label are as if I've never touched them! When the worker is complete, the Close button is enabled, so I know its finished. Anybody got any pointers/thoughts on this because I've been battling with this for a day and a half so far. I'm using the same technique as I've used elsewhere in the app to do similar backgroundworker progress updates, but this one refuses to work properly.
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May 2, 2009
I am using a class with below code, the question is how to update the label's value at UI thread from the backgroundworker?
Imports MySql.Data.MySqlClient
Public Class clsBackGroundWorker
[code]....
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Jan 27, 2010
im sorry if this has been asked before.but i couldent find it in my first look i have a form that runs a query on a mysql database but as it runs the query the form stops responding till it finishes sooo i had the smart idea of putting it in a back ground worker..
GREAT i thot i had it working it all seemed to go greeat then i noticed when i try to change the label text on the form to corispond to the info it got... it wont work it give me a cross threading error....
how to cross thread between the back ground worker and the origial form..
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Jul 29, 2009
I wanna sleep a second thread of BackgroundWorker. I tried to use Me.Dispatcher.Thread.Sleep(500) in DoWork event, but it fails.
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Apr 17, 2012
I have some classes right now that I have that I reuse for Client/Server programming. I'm using Thread in these classes though for monitoring for things being written to the network streams and stuff like that. I'm just not sure if I should be using the background worker class instead. I'm also using TCPClient and Listener classes, should I be using sockets directly? I guess it would all depend on the flexibility I would need in a given application's specs.
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